1. Field of the Invention
The invention relates to a device for indicating the need for service or inspection of a motor vehicle, wherein the service or inspection is carried out whenever the vehicle has travelled certain mileage. An indicator is provided which, at the end of the prespecified mileage, generates a visible or audible signal.
2. Description of the Prior Art
For the decontamination of exhaust gases of motor vehicles, exhaust gas catalysts have lately been developed which are installed in the exhaust system. Such catalysts are generally no longer effective after having been in use for a certain period of time and must then be replaced by fresh ones. Therefore, the need for a device exists which after a certain mileage, generally 12,500 km (i.e., 7767.5 miles), indicates by means of a visible or audible signal the replacement to be carried out, and in which the signal can only be extinguished after replacement of the catalysts, so as to permit a control of the replacement by the traffic police or other governmental authorities.
To indicate the need for a service or inspection to be carried out after a certain mileage has been covered, a number of devices are already known. In most of these devices, a switch contact is provided in connection with the odometer of the motor vehicle, and the switch contact is actuated after a specific mileage to generate a visible or audible signal. Such devices have the disadvantage that, during continuing operation, the signal is extinguished after a number of miles, regardless of whether or not the service or inspection work has been carrried out. Another known device contains a cam driven by an odometer, which cam acts upon a unilaterally clamped-in leaf spring whose free end engages a groove in a spring-loaded indication drum. After a specific mileage the leaf spring is disengaged from the indicating roller by the cam, which therefore pivots into its indicating position. A considerable disadvantage of this device is that, when the service or inspection work must be carried out somewhat earlier than required, the signal is nevertheless switched on after the prespecified mileage has been reached. Moreover, a switching-off of the notice is only possible after a certain mileage has been covered. Besides, such a device presents the disadvantage of being bulky and must be placed in a casing of its own, outside the tachometer. Electrochemical elements are used for measurement mileage travelled by rental automobiles to calculate rental fees in U.S. Pat. No. 3,665,397 and 3,754,122.